Sole for walking cast

ABSTRACT

A sole for a walking cast is described having a base plate embedded in the cast with a flexible convex shaped leaf spring attached to the base plate which is deflected to absorb the shock of the cast striking the ground and to deflect with the increasing application of the patient&#39;&#39;s weight. A resilient element is positioned between the base plate and the spring to limit the deflection according to the weight of the patient.

United States Patent Tunstall [4 1 Aug. 1, 1972 [54] SOLE FOR WALKING CAST [72] Inventor: Don M. Tunstall, 1016 Larson Bldg., Yakima, Wash. 98901 [22] Filed: Sept. 4, 1970 [21] Appl. No.: 69,734

[52] US. Cl ..128/83.5 [51] Int. Cl. ..A6lf 5/04 [58] Field of Search ..128/83.5, 83

[56] References Cited UNITED STATES PATENTS 3,494,355 2/1970 Wolpow ..l28/83.5

FOREIGN PATENTS OR APPLICATIONS 1,014,877 6/1952 France ..128/83.5

OTHER PUBLICATIONS Lewin Walking Heel, Zimmer Fracture Appliances, pg. 116, Feb. 1, 1947. Walking Iron, I-LE. Snyder, Journal A.M.A. April 23, 1938, pp. 1,341, 1,342.

Primary ExaminerRichard A. Gaudet Assistant Examiner-J. Yasko Att0meyWells, St. John & Roberts [57] ABSTRACT A sole for a walking cast is described having a base plate embedded in the cast with a flexible convex shaped leaf spring attached to the base plate which is deflected to absorb the shock of the cast striking the ground and to deflect with the increasing application of the patients weight. A resilient element is positioned between the base plate and the spring to limit the deflection according to the weight of the patient.

8 Claims, 4 Drawing Figures SOLE FOR WALKING CAST BACKGROUND OF THE INVENTION This invention relates to walking casts and more particularly to soles for walking casts to facilitate the ease of walking during the ambulatory period.

During the ambulatory treatment of fractures of the lower extremities, particularly ankles and foot members, a plaster cast is placed on the extremity to greatly limit movement of the ankle and to provide additional support. Casts of this type are generally applied when early weight bearing is desirable without motion of the joints, particularly the ankle. The cast is generally constructed of a plaster impregnated bandage to form a rigid support about the extremity.

Frequently a hard rubber cushion is mounted to the base of the cast to protect the bottom of the cast and to provide some assistance to the patient in attempting to walk with the cast in place. Most patients have found that such a hard rubber cushion is not totally satisfactory since the hard rubber cushion still transmits a substantial amount of the shock causing a great deal of discomfort. Furthermore, the hard rubber cushion is usually located immediately below the heel requiring the patient to rotate the cast outward as his weight is supported on the cushion while walking. This causes tension on the injured extremity which can be quite painful and discomforting.

Many different types of walking heels or soles have been suggested, but none appear to have provided substantial relief to the patient. Examples of devices that have been suggested are disclosed in U.S. Pat. No. 2,341,963; 2,762,367, and 2,888,919.

One of the principal objects of this invention is to provide a sole for a walking cast that materially absorbs the shock encountered by the cast striking the ground and for enabling the patient to walk with the cast without having to twist the cast to the side during each stride.

An additional object of this invention is to provide a sole for a walking cast that may. be economical to manufacture enabling the sole to be readily available to the general public.

A further object of this invention is to provide a sole for a walking cast in which the sole is specifically designed to match the weight of the patient to obtain uniform results.

An additional object of this invention is to provide a sole for a walking cast that is capable of simultaneously absorbing the shock while enabling the cast to rock forward simulating a more natural stride.

These and other objects and advantages of this invention will become apparent upon the reading of the following detailed description of a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a side view of a section of a walking cast having a sole thereon embodying the principal features of the invention;

F IG. 2 is a vertical longitudinal sectional view through a portion of the walking cast illustrating the engagement and deflection of the sole with the ground under the full weight of the patient;

FIG. 3 is an enlarged vertical longitudinal sectional view of the sole illustrating its principal features; and

FIG. 4 is a vertical transverse sectional view taken along line 4-4 in FIG. 3.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Now referring in detail to the drawings, there is shown in FIG. 1 a sole identified by the numeral 10 mounted on the bottom of a walking cast 11. Frequently the cast is constructed by initially placing a knit stocking over the foot. Then plaster of paris embedded gauze is wrapped around the foot. Then, after drying the walking cast is positioned against the sole of the foot and additional gauze is wrapped around the cast at the foot and heel and then allowed to dry.

The cast generally has an upper leg portion 13 and a lower foot portion 14. The foot portion 14 has a heel section 15, a toe section 16 and an instep section 17 between the heel and toe section 17.

The sole 10 is embedded in the walking cast during its construction and projects below the walking cast for engaging the ground. The sole 10 has an elongated base plate 20 that is embedded in the cast and extends from the heel section 15 through the instep section 17 to the toe section 16. The elongated base plate 20 should be made of a rather rigid material such as metal or high strength reinforced plastic. The base plate 20 has a heel end 21 and a toe end 22. An elongated transverse slot 24 (FIG. 3) is formed through the base plate 20 at toe end 22.

The sole 10 further includes a leaf spring 26 that is formed in a convex shape as shown in the drawing having a flared end 27 fixed to the heel end 21 by rivets 28. The spring 26 has a free front end 30 that extends through the transverse slot 24. The leaf spring is bowed in an arch having a lower projection that extends below the cast terminating at an apex 32 of the leaf spring. An arch shaped cavity 31 is formed between the base plate 20 and the spring 26.

A non-skid tread 34 is mounted on the lower surface of the leaf spring to provide a substantial frictional contact with the ground. The tread may be made of a rubber or synthetic plastic material that has a high frictional coefficient. The tread 34 is secured to the lower surface of the leaf spring 26 by screws 35. Alternatively, the tread may be applied with adhesive. The tread 34 has ends 37 and 38 that extend into and are embedded in the heel and toe sections 15 and 16 respectively.

A shield 40 (FIG. 3) is mounted on the upper surface of the base plate 20 at the toe end 22 forming a cavity 41 for receiving the free end 30 of the leaf spring to permit the leaf spring to deflect as the patients weight is applied to the sole.

An important feature of the sole 10 is the provision of a calibrated resilient element 44 mounted in the cavity 31 between the base plate 30 and the apex of the leaf spring 36 for controlling the deflection of the leaf spring 26 and to maintain the leaf spring in a convex configuration to enable the patient to rock forward on the sole to simulate the natural action of the ankle while simultaneously absorbing the shock of the walk ing cast striking the ground.

The calibrator resilient element 44 has a selected density and cross section that is related to the weight of the patient so that the sole can be specifically designed for each patient. The resilient element includes a top surface 46 that engages the base plate 20 and a bottom curve surface 47 that engages the spring 26. A bolt 48 (FIG. 4) attaches the resilient element 44 to the base plate 20. Various densities and cross sections of the resilient element 44 may be utilized depending upon the weight of the patient. If the patient weighs approximately 130 pounds, then the resilient element will be selected having less density than one selected for a person weighing 200 pounds so that the amount of deflecting of the leaf spring 26 will remain substantially constant independently of the weight of the patient. It has been found that a resilient foam material generally referred to as iron foam serves as a good resilient element 44. Stated in another way, the amount of elasticity of the resilient element 44 is inversely proportioned to the relative weight of the patient. This means that for a heavier person the resilient element 44 will be somewhat stiffer than that utilized for a lighter person.

Flexible plastic or rubber side walls 50 and 51 (FIG. 4) are attached to the base plate and extend downwardly to the leaf spring 26 enclosing the cavity 31 so that dust, dirt and the like will not interfere with the resilient nature and characteristics of the sole 10.

Alternatively, the sole 10 could be attached to the sole after the cast is formed, although it appears preferable to embed the sole in the bottom of the cast while the walking cast is being molded to the foot.

When the patient desires to walk with the cast, he merely lifts the leg and cast and projects it forward until the sole strikes the ground. The shock of the impact is absorbed by the leaf spring 26 and the resilient element 44. As the patient moves forward increasing the weight on the sole, the leaf spring deflects further, with end 30 moving further into the cavity 41. Also, the resilient element 44 is partially compressed maintaining the leaf spring in a convex shape. This enables the patient to rock forward on the sole without having to substantially twist the cast to the side.

It should be understood that the above described embodiment is simply illustrative of the principles of this invention and that numerous other embodiments may be readily devised by those skilled in the art without deviating therefrom. Therefore, only the following claims are intended to define this invention.

What is claimed is:

1. A sole for a walking cast enclosing a human foot comprising:

a base plate affixed to the walking cast;

a convex leaf spring mounted to the base plate for resiliently deflecting the weight of the person on the cast when it is exerted on the sole to absorb the shock when the sole strikes the ground; a slot formed in the base plate transverse to the direction of the plate; and the convex leaf spring has one end fixed to the base plate and a free end slidably mounted in the slot to permit the leaf spring to resiliently deflect with the free end sliding in the slot. 2. A sole as defined in claim 1 wherein a non-skid tread is affixed to the convex leaf spring for engaging if fi i as defined in claim 1 further comprising a resilient element mounted between the base plate and the leaf spring that is sufficiently compressible to enable the leaf spring to deflect while the leaf spring is maintained in a convex shape to enable the walking cast to rock forward while the leaf spring is deflected.

4. A sole as defined in claim 3 wherein the resilient element has a modulus of elasticity that is selected in inverse proportion to the weight of the person wearing the cast to permit the leaf spring to deflect a desired amount in response to said weight.

5. A sole as defined in claim 1 wherein the base plate has a heel end and a toe end with the transverse slot formed adjacent the to end and wherein the fixed end of the convex leaf spring is fixed to the heel end of the plate and the free end extends through the transverse slot in the toe end of the base plate.

6. A sole as defined in claim 1 further comprising:

a shield mounted on the upper surface of the base plate forming a cavity communicating with the slot receiving the free end of the leaf spring to permit the leaf spring to deflect as weight is applied to the sole.

7. A sole for a walking cast enclosing a human foot comprising:

a base plate affixed to the walking cast;

a convex leaf spring having one end affixed to the base plate with a bowed intermediate portion extending from the affixed one end beneath the base plate to a free end for resiliently deflecting when the weight of the person is exerted on the sole to absorb the shock when the sole strikes the ground; and

a resilient element mounted between the base plate and the bowed intermediate portion of the leaf spring that is sufficiently compressible to enable the leaf spring to deflect intermediate the ends while the leaf spring is maintained in a convex shape to enable the walking case to rock forward while the leaf spring is deflected.

8. A sole as defined in claim 7 wherein the resilient element has a modulus of elasticity that is selected in inverse proportion to the weight of the person wearing the cast to permit the leaf spring to deflect intermediate the ends a desired amount in response to said weight. 

1. A sole for a walking cast enclosing a human foot comprising: a base plate affixed to the walking cast; a convex leaf spring mounted to the base plate for resiliently deflecting the weight of the person on the cast when it is exerted on the sole to absorb the shock when the sole strikes the ground; a slot formed in the base plate transverse to the direction of the plate; and the convex leaf spring has one end fixed to the base plate and a free end slidably mounted in the slot to permit the leaf spring to resiliently deflect with the free end sliding in the slot.
 2. A sole as defined in claim 1 wherein a non-skid tread is affixed to the convex leaf spring for engaging the ground.
 3. A sole as defined in claim 1 further comprising a resilient element mounted between the base plate and the leaf spring that is sufficiently compressible to enable the leaf spring to deflect while the leaf spring is maintained in a convex shape to enable the walking cast to rock forward while the leaf spring is deflected.
 4. A sole as defined in claim 3 wherein the resilient element has a modulus of elasticity that is selected in inverse proportion to the weight of the person wearing the cast to permit the leaf spring to deflect a desired amount in response to said weight.
 5. A sole as defined in claim 1 wherein the base plate has a heel end and a toe end with the transverse slot formed adjacent the to end and wherein the fixed end of the convex leaf spring is fixed to the heel end of the plate and the free end extends through the transverse slot in the toe end of the base plate.
 6. A sole as defined in claim 1 further comprising: a shield mounted on the upper surface of the base plate forming a cavity communicating with the slot receiving the free end of the leaf spring to permit the leaf spring to deflect as weight is applied to the sole.
 7. A sole for a walking cast enclosing a human foot comprising: a base plate affixed to the walking cast; a convex leaf spring having one end affixed to the base plate with a bowed intermediate portion extending from the affixed one end beneath the base plate to a free end for resiliently deflecting when the weight of the person is exerted on the sole to absorb the shock when the sole strikes the ground; and a resilient element mounted between the base plate and the bowed intermediate portion of the leaf spring that is sufficiently compressible to enable the leaf spring to deflect intermediate the ends while the leaf spring is maintained in a convex shape to enable the walking case to rock forward while the leaf spring is deflected.
 8. A sole as defined in claim 7 wherein the resilient element has a modulus of elasticity that is selected in inverse proportion to the weight of the person wearing the cast to permit the leaf spring to deflect intermediate the ends a desired amount in response to said weight. 